Did the Earth move for you? The image in your browser should — well, it should have done a barrel roll. As often happens, the Internet was filled with speculation when people began to notice it on Thursday. Many Twitter posts asked if it was a takeoff on Apple’s iPads, with their built-in accelerometers so that their screens turn if you turn the device (the New York Times’ Bits blog called the effect “Siri-like”). At least one blogger suggested Google was invoking Nintendo’s “Star Fox.”

No such notions, says Google, which sent us this explanation:

“Today’s fun query, ‘do a barrel roll,’ was created by a Google software engineer with the primary goal of entertaining users — while showcasing the power of CSS3, a presentation feature of modern browsers. The “do a barrel roll” query, which causes the search page to spin, will remain in place for a while.”

(By the way, Google says you may not see the effect in older browsers. Newer ones support HTML5, the newest version of the code that makes online content work.)